York YZ Magnetic Bearing Centrifugal Chiller User guide

Brand: York

Model: YZ Magnetic Bearing Centrifugal Chiller

Type: User guide

ENGINEERING GUIDE

YORK

YZ Centrifugal Chiller

Form: 161.01-EG1 (0819)

MODEL YZ MAGNETIC BEARING CENTRIFUGAL CHILLER

Style A

530 through 5010 kW

(150 through 1425 Tons)

Utilizing R-1233zd

YZ Engineering Guide

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Table of Contents

Nomenclature ........................................................................................................................................ 3

Introduction ........................................................................................................................................... 4

Unit Components .................................................................................................................................. 6

Equipment Overview ............................................................................................................................. 8

Codes and Standards ......................................................................................................................... 14

Chiller Options .................................................................................................................................... 16

Application Data .................................................................................................................................. 17

Unit Weights & Dimensions................................................................................................................. 22

Visit YORK.com/Next for more information

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Nomenclature

SYSTEM

YZ – MA033 AN030 P042N A

MOTOR

MA 033 AA

COMPRESSOR

AN 030NA – AA

VARIABLE SPEED DRIVE

P 042 NA C A – 6 6

HEAT EXCHANGER

FA 21 12 – A2Z *** – 2 CA 1 G LR B

VSD Family

VSD Size Code

Filter (N-no filter, H-harmonic filter)

VSD Cooling

Product Family

Motor Name

Compressor Name

Unit Mod Level

VSD Name

Motor Family

Motor Size Code

Motor Configuration Level

Compressor Family

Compressor Size Code

Compressor Configuration Level

Frequency

Voltage

Sediment Accumulator

Heat Exchanger Family

Nominal Diameter

Nominal Length

Bundle Code

Tube Type

Hinges

Nozzle Arrangement

Water Connection Type

Waterside DWP

Waterbox Family

Number of Passes

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Introduction

The YORK® YZ Magnetic Bearing Centrifugal Chiller is a revolutionary advancement that challenges everything about

conventional chiller design. The result is a chiller fully optimized for ultimate performance with a next generation low-

GWP (global warming potential) refrigerant, delivering superior real-world performance and a new definition of

sustainability. The YORK® YZ Chiller is available from multiple global factories to meet regional customers’ needs.

EFFICIENCY

Johnson Controls pioneered the term “real-world efficiency” to illustrate the energy-saving potential of focusing on chiller

performance during off-design conditions. Off-design conditions are not only seen at part-load, but at full-load operation

as well, by taking advantage of reduced entering condenser water temperatures (ECWTs). These conditions are where

chillers operate up to 99% of the time, and where operating costs add up. YZ chillers are designed to operate on a

continuous basis with cold ECWT and full condenser flow at all load points, taking full advantage of real-world conditions.

YZ chillers offer the most efficient real-world operation of any chiller, meaning lower operating costs and an excellent

return on your chiller investment.

Actual chiller efficiency cannot be determined by analyzing the theoretical efficiency of any one chiller component. It

requires a specific combination of heat exchanger, compressor, and motor performance to achieve the best system

efficiency. YZ technology matches chiller system components to provide maximum chiller efficiency under actual – not

just theoretical – operating conditions. Now with the YORK® YZ, efficiency is improved up to an impressive 7% at part-

load and as much as an additional 5% at full-load versus our most efficient previous designs.

BETTER EFFICIENCY IN EVERY OPERATING CONDITION

The YZ chiller has been designed to take full advantage of colder cooling tower water temperatures, which are naturally

available during most operating hours. Considerable energy savings are available by letting tower water temperature

drop, rather than artificially holding it above 19°C (65°F), especially at low load, as some chillers require.

Since the vast majority of its operating hours are spent at off-design conditions, a chiller should be chosen not only to

meet the full-load design, but also for its ability to perform efficiently at lower loads, lower tower water temperatures, and

even higher leaving evaporator water temperatures. It is not uncommon for chillers with the same full-load efficiency to

have an operating cost difference of over 10% due to differences in part-load efficiencies.

Part-load is important to an owner’s operating budget, this information has been standardized within the AHRI

Certification Program in the form of an Integrated Part Load Value (IPLV), and Non-Standard Part Load Value (NPLV).

Additionally, looking at annual energy costs that use weather data specific to your city, you can get a better understanding

of the efficiency benefits the YORK® YZ offers across a wide range of operating conditions. This more detailed analysis

also takes into account actual building load profiles to provide a more accurate view of chiller operating cost. Part-load

performance data should be requested by the customer for each job using its own design criteria.

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RELIABILITY

Designed for the most reliable chillers we have ever made, the YORK® YZ magnetic bearing compressor achieves

superior performance because it is based on a successful line of efficient YORK® compressors. With fewer moving parts,

YORK® compressors have proven to be durable in numerous applications, especially where minimal downtime is a

critical concern. The lubrication-free, non-contact design of the YORK® YZ provides system simplicity and reliability that

far exceeds continuous-contact-oil and refrigerant-lubricated bearing chiller designs.

The majority of chiller components on YZ chillers have been time tested on the tens of thousands of air-cooled and water-

cooled YORK® chillers operating globally. The YZ chiller employs the most advanced driveline available - an active

magnetic-bearing drive to levitate the driveshaft. The result is frictionless operation and 80% fewer moving parts than

oil-lubricated or refrigerant-lubricated systems, which is why we have used this type of driveline in our mission-critical

chillers since 1998.

The YZ chiller incorporates service design principles that are consistent with our family of centrifugal chillers. We made

sure that this chiller, and specifically the driveline, was field serviceable by a single source supplier, who also happens

to be the industry’s largest service force: our own Johnson Controls service team.

AHRI CERTIFICATION PROGRAM

The performance of the YZ chiller has been certified by the Air Conditioning, Heating and Refrigeration Institute (AHRI)

as complying with the certification sections of the latest issue of AHRI Standard 550/590. Under this Certification

Program, chillers are regularly tested in strict compliance with this Standard. This provides an independent, third-party

verification of chiller performance.

COMPUTERIZED PERFORMANCE RATINGS

Each chiller is custom-matched to meet the individual building load and energy requirements. A variety of standard heat

exchangers and pass arrangements are available to provide the best possible match.

It is not practical to provide tabulated performance for each combination, as the energy requirements at both full- and

part-load vary significantly with each heat exchanger and pass arrangement. Computerized ratings are available through

each Johnson Controls sales office. Each rating can be tailored to a specific job requirement, and is part of the AHRI

Certification Program.

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Unit Components

Suction Line

Endsheet

OptiView™ Control

Panel

Condenser

Sight

Glass

Lockout Handle

Variable Speed

Drive

Discharge Line

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Unit Components (Continued)

VSD Coolant

Reservoir

Refrigerant

Purge Unit

Compact

Waterbox

Evaporator

Direct Drive

Compressor Motor

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Equipment Overview

YORK® YZ Centrifugal Chillers are completely factory-packaged including the compressor, motor, VSD, OptiView™

control center, evaporator, condenser, purge unit, and all interconnecting unit piping and wiring.

When selected, the initial charge of refrigerant can be supplied for each chiller from the factory. Actual shipping

procedures for the chiller will depend on a number of project-specific details. YZ chillers are designed to keep installation

costs low. Where installation access is not a problem, the unit can be shipped completely packaged including the unit-

mounted variable speed drive, requiring minimal piping and wiring to complete the installation.

At start-up, the services of a Johnson Controls factory-trained, field service representative are required to supervise or

perform the final leak testing, charging, initial start-up, and concurrent operator instructions.

COMPRESSOR

Note: Please refer to the YZ Operations & Maintenance Manual (161.01-OM1) for a complete description of features and

functionality.

The compressor is a single-stage centrifugal design directly driven by a hermetically-sealed motor with a VSD. A cast-

aluminum, fully-shrouded impeller is mounted directly to the motor shaft. Impeller seals employ a labyrinth geometry,

sized to provide minimal thrust loading on the impeller throughout the operating range. The impeller is dynamically

balanced and overspeed tested for smooth, vibration-free operation.

CAPACITY CONTROL

Capacity control is achieved by the combined use of variable speed control and mechanical flow regulation to provide

fully modulating control from maximum to minimum load. For normal air conditioning applications, the chiller can adjust

capacity from 100% to 10% of design, without the use of hot gas bypass (HGBP). For each condition, the capacity control

devices will be automatically adjusted to maintain a constant leaving chilled liquid temperature at optimized efficiency,

based on information fed by sensors located throughout the chiller.

YZ chillers are equipped with sophisticated capacity control as standard. Our capacity control is a patented combination

of centrifugal chiller hardware and software that expands the chiller operating range and improves chiller performance.

The capacity control continuously monitors the characteristics of the compressor discharge gas and optimizes the diffuser

spacing to minimize gas-flow disruptions from the impeller.

MOTOR

The compressor motor is a hermetically-sealed, high-speed induction motor supported by active magnetic bearings. The

bearing design provides a completely lubrication-free operating system. The motor rotor and stator are cooled by a

pressure driven refrigerant loop to maintain acceptable operating temperatures.

The active magnetic bearings are equipped with balancing systems to ensure smooth and reliable operation. In the event

of a power failure, the magnetic bearings will remain in operation throughout the compressor coast-down using an

uninterruptable power supply. Mechanical bearings are included as backup to the magnetic bearings and are designed

for rare emergency touchdown situations where both the main power and uninterruptable power supply fail.

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VARIABLE SPEED DRIVE

Note: Please refer to the YZ Operations & Maintenance Manual (161.01-OM1) for a complete description of features and

functionality.

A variable speed drive is factory-packaged and mounted on the YZ chiller. It is designed to vary the compressor motor

speed by controlling the frequency and voltage of the electrical power to the motor. The capacity control logic shall

automatically adjust motor speed and compressor diffuser geometry for maximum part load efficiency by analyzing

information fed to it by sensors located throughout the chiller. The variable speed drive is mounted in a NEMA-1/IP22

enclosure with all power and control wiring between the drive and chiller factory-installed. The chiller uses a single-point

power connection with a circuit breaker disconnect. Electrical lugs for incoming power wiring are provided.

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The variable speed drive provides automatic displacement power factor correction to 0.95 or better at all load conditions.

Separate displacement power factor correction capacitors are not required. The displacement power factor is 0.98 or

better when the optional harmonic filter is provided. Additionally, variable speed drives provide the following advantages:

 Lowest chiller operating cost through part load energy savings.

 Soft start with input current less than full load current.

 Smooth acceleration reduces stresses on motor and driveline.

 Rugged and reliable with no moving parts.

Standard features include: a door interlocked lockable circuit breaker; UL/cUL listed and CE approved ground fault

protection; over-voltage and under-voltage protection; 3-phase sensing motor over-current protection; single-phase

protection; insensitive to phase rotation; over-temperature protection and readouts of important values on the OptiView™

control panel.

OPTIVIEW™ CONTROL CENTER

Note: Please refer to the YZ Operations & Maintenance Manual (161.01-OM1) for a complete description of features and

functionality.

The YORK® OptiView™ Control Center is a factory mounted, wired and tested microprocessor based control system for

centrifugal chillers. It provides control of chiller operation and monitoring of chiller sensors, actuators, relays and switches.

As part of the capacity control logic, OptiView™ controls the leaving chilled liquid temperature and adjusts the motor

current via control of the Variable Geometry Diffuser (VGD) and Variable Speed Drive (VSD).

The panel comes configured with a full screen graphic display mounted in the middle of a keypad interface with soft keys.

The operator may view a graphical representation of the historical operation of the chiller as well as the present operation.

The locations of various chiller parameters are clearly marked, and instructions for specific operations are provided on

many of the screens. To prevent unauthorized changes of setpoints and operating conditions, security access is provided

with three different levels of access and passwords.

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The graphic display also allows information to be represented in both SI and Imperial units of measure, and has the

ability to display many languages.

OptiView™ continually monitors the system operation and records the cause of any shutdowns (safety, cycling or

normal). This information is recorded in memory and is preserved even through a power failure condition, so the user

may recall it for viewing at any time. During operation, the user is continually advised of the operating conditions by

various status and warning messages. By providing a common networking protocol through the Building Automation

System (BAS), YORK® chillers not only work well individually, but also as a part of the building system. This networking

protocol allows increased remote control of the chiller, as well as 24-hour performance monitoring via a remote site. In

addition, compatibility is maintained with the present network of BAS communications. Both of these remote control

capabilities allow for the standard Energy Management System (EMS) interface:

1. Remote Start

2. Remote Stop

3. Remote leaving chilled liquid temperature setpoint adjustment

4. Remote current limit setpoint adjustment

5. Pulse Width Modulation

6. Remote “Ready to Start” Contacts

7. Safety Shutdown Contacts

8. Cycling Shutdown Contacts

HEAT EXCHANGERS

Shells

Evaporator and condenser shells are fabricated from rolled carbon steel plates with fusion welded seams or carbon steel

pipe. Carbon steel tube sheets, drilled and reamed to accommodate the tubes, are welded to the end of each shell.

Intermediate tube supports are fabricated from carbon steel plates, and drilled and reamed to eliminate sharp edges.

The refrigerant side of each shell is designed, tested, and stamped in accordance with local pressure vessel codes.

Tubes

Heat exchanger tubes are copper alloy high-efficiency, externally and internally enhanced to provide optimum

performance. Utilizing the “skip-fin” tube design provides a smooth internal and external surface at each intermediate

tube support. This provides extra wall thickness (up to twice as thick) and non work-hardened copper at the support

location, extending the life of the heat exchangers. Each tube is expanded into the tube sheets providing a leak-proof

seal, and is individually replaceable.

Evaporator

The evaporator is a patented hybrid falling-film type heat exchanger. It contains a balance of flooded and falling-film

technology to optimize efficiency, minimize refrigerant charge, and maintain reliable control. A specifically designed spray

header provides uniform distribution of refrigerant over the entire shell length to yield optimum heat transfer. A suction

eliminator is located above the tube bundle to prevent liquid refrigerant carryover into the compressor. A 38 mm (1.5")

liquid level sight glass is conveniently located on the side of the shell to aid in determining proper refrigerant charge. The

evaporator shell contains a dual refrigerant relief valve arrangement or a single relief valve arrangement if the chiller is

supplied with the optional refrigerant isolation valves. A 25.4 mm (1") refrigerant charging valve is provided for service

access.

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Condenser

The condenser is a shell and tube type heat exchanger with a discharge gas baffle to prevent direct high velocity

impingement on the tubes. The baffle is also used to distribute the refrigerant gas flow properly for the most efficient heat

transfer. An integral subcooler is located at the bottom of the condenser shell, providing highly effective liquid refrigerant

subcooling to provide the highest possible cycle efficiency. A 38 mm (1.5") liquid level sight glass is conveniently located

on the side of the shell to aid in determining proper refrigerant charge. The condenser contains dual refrigerant relief

valves.

Waterboxes

The removable waterboxes are fabricated of steel. Integral steel water baffles are located and welded within the waterbox

to provide the required pass arrangements. Stub-out water nozzle connections welded to the waterboxes are suitable

for ANSI/AWWA C-606 couplings, welding or flanged, and are capped for protection during shipment. Plugged 19 mm

(3/4") drain and vent connections are provided in each waterbox.

Water Flow Switches

Thermal or differential pressure type water flow switches are factory mounted in the evaporator and condenser water

nozzles, and are factory wired to the OptiView™ control panel.

Refrigerant Flow Control

Refrigerant flow to the evaporator is controlled by the YORK® variable orifice control system. Liquid refrigerant level is

continuously monitored to provide optimum subcooler, condenser and evaporator performance. The variable orifice

electronically adjusts to all real-world operating conditions, providing the most efficient and reliable operation of

refrigerant flow control without the use of a refrigerant pump.

Refrigerant Purge Unit

The purge is designed to meet the ASHRAE Standard 147 where at most one unit mass of refrigerant is purged per one

unit mass of air removed by the unit. This automatic, self-contained, high-efficiency purge unit collects non-condensable

gases to be removed from the chiller. The YORK® purge is factory assembled, mounted, piped, and wired, and operates

automatically. Purge exhaust cycles are monitored, and if excessive, provide warning of a potential system leak to the

OptiView™ Control Center.

ISOLATION MOUNTING

The unit is provided with four vibration isolation mounts of nominal 25.4 mm (1") operating height. The isolators have a

neoprene pad to contact the foundation, bonded to a steel plate. The vibration isolation pad assemblies mount under

steel plates welded to the chiller tube sheets.

Optionally, spring isolation mounting is available instead of standard isolation mounting pads. Four level-adjusting,

spring-type vibration isolator assemblies with non-skid pads are provided for field-installation. Isolators are designed for

25.4 mm (1") of deflection.

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REFRIGERANT CONTAINMENT

The standard unit has been designed as a complete factory-packaged chiller, which minimizes the joints from which

refrigerant can leak. The entire assembly is thoroughly leak tested at the factory prior to shipment. The YZ chiller includes

service valves conveniently located to facilitate transfer of refrigerant to a remote refrigerant storage/recycling system.

Optional factory-installed isolation valves in the compressor discharge line and refrigerant liquid line allow isolation and

storage of the refrigerant charge in the chiller condenser.

FACTORY TESTING

Johnson Controls has the ability to factory performance test every type of chiller that we engineer and manufacture.

Testing options, including performance, vibration, and sound, can be performed as factory or remote customer witness

tests.

SMART EQUIPMENT

Smart Equipment by Johnson Controls allows the connection of data streams from equipment to the cloud, providing

unprecedented insights into operations. Smart Equipment helps maximize system control for greater efficiency, extended

equipment life and reduced operating costs. The YORK® YZ chiller has controls embedded at the factory to allow the

chiller to connect seamlessly to a controls system. On-board controls that support cloud-based data analytics, including

fault detection, enables proactive maintenance and minimizes downtime.

YORK® SMART CONNECTED CHILLERS

YORK® Smart Connected Chiller functionality feeds YZ chiller data to a secure, cloud-based dashboard, enabling

analysis of historical data to diagnose the chiller, observe long-term trends, and investigate potential issues. The

dashboard collects status-related data warnings, cycling, and safety fault codes. Advanced algorithms detect problems

such as condenser or evaporator tube fouling or low refrigerant charge. A more strategic approach to maintenance can

be implemented to stay a step ahead of emergencies to save time and money.

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SHIPMENT

Each unit can be broken down into several form shipment configurations for ease of transportation and installation. For

all broken down shipment options, the unit is first factory assembled, refrigerant piped, wired and leak tested; then

disassembled according to the shipment option selected.

Protective covering is furnished on the OptiView™ and VSD. Water nozzles are capped with fitted plastic enclosures.

Then the entire unit is protected with industrial-grade, reinforced shrink-wrap covering.

Form 1 – Unit is shipped as one assembly with refrigerant charge inside the unit.

Form 2 – Unit is shipped as one assembly with refrigerant charge shipped separately.

Form 3 – Driveline separate from shells. Shipped as three major subassemblies with refrigerant charge shipped

separately. This form is best used when height is a limiting dimension to enter the installation site.

 Driveline (motor/compressor assembly)

 Evaporator/Condenser shell assembly – not skidded

 Variable Speed Drive

Form 7 – Driveline separate from split shells. Shipped as four major subassemblies, with refrigerant charge shipped

separately. This form is best used when the chiller must fit through a tight space, limited by multiple dimensions.

 Driveline (motor/compressor assembly)

 Evaporator – not skidded

 Condenser – not skidded

 Variable Speed Drive

Form 11 – Unit shipped as two major subassemblies, with refrigerant charge shipped separately. This form is best used

when width is a limiting dimension to enter the installation site.

 Condenser side assembly (Condenser/OptiView™/Variable Speed Drive) – not skidded

 Evaporator side assembly (Evaporator/Driveline/Magnetic Bearing Controller) – not skidded

Codes and Standards

Chiller standards and codes vary based on factory source. Any of the standards and codes listed below can be met when

ordering the YZ chiller. Work with your local sales contact for a unit that will meet your local codes and standards.

PERFORMANCE & ENERGY STANDARDS

 ASHRAE 90.1

 AHRI Standard 550/590

 IECC – International Energy Conservation Code

 GBCI – Green Business Certification Inc.

 Eurovent (EN14511, EN14825)

 GB 18430.1

 GB 19577/GB 50189

 GB/T 50378

 MEPS – Minimum Energy Performance Standards

 ECBC – Energy Conservation Building Code

 Greenmark

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 BEC – Business Environment Council

 SASO – Saudi Standards, Metrology and Quality Organization

 ESMA – Emirates Authority for Standardization and Metrology

 LEED EA4 enhanced refrigerant management credit

 BREEAM Refrigerant Credit – Building Research Establishment Environmental Assessment Method

SOUND RATINGS

 AHRI 575

 ISO 9614/3744

 JB/T 4330

PRESSURE VESSEL CODES

 ASME Boiler and Pressure Vessel Code – Section VIII

 PED – European Pressure Equipment Directive

 NB/T 47012

 KHK – High Pressure Gas Control Law

ELECTRICAL CODES

 c/U.L. – Underwriters Laboratory

 N.E.C. – National Electrical Code

 CE – Directive 93/68/EEC

 IP – Ingress Protection

 GB 5226.1

 ETL – Electrical Testing Labs

SAFETY CODES

 ASHRAE 15 – Safety Code for Mechanical Refrigeration

 ASME

 Safety Code for Mechanical Refrigeration (EN 378-2/A2)

 Machinery Directive (2006/42/EC)

 EMC Directive (2004/108/EC)

 Safety of machinery – Electrical Equipment of Machine (EN 60204-1)

 GB 25131

MANUFACTURING REQUIREMENTS

 Manufactured in an EN ISO 9001 accredited organization

 Conform to CE Testing Services for construction of chillers and provide CE listed mark

 EN 61000-6-2:2005 and EN 61000-6-4:2007 compliance for use in an industrial environment

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Chiller Options

ITEM

DESCRIPTION

STANDARD

OPTIONAL

VSD

Harmonic Filter

None

Input harmonic filter

Incoming customer wiring

60 Hz: 460V, 400V, 380V

50 Hz: 415V, 400V, 380V

VSD cooling heat exchanger protection

(for condenser fluid lines)

None

Sediment accumulator

Heat Exchangers

Tube wall thickness

0.635 mm (0.025")

0.711 mm and 0.889 mm

(0.028" and 0.035")

Factory tube testing

None

Factory Eddy current

testing

Evaporator thermal insulation

None

19 mm, 25.4 mm

, 32

, and 38 mm (3/4”, 1”,

1.25”, 1.5”) standard

thickness

Waterbox

Customer piping connections

Grooved

Flanges

Waterbox design

Compact

Marine

Design working pressure

1034 kPa (150 psig) DWP

2070 kPa (300 psig) DWP

Hinges

None

1034 kPa & 2070 kPa

(150 psig & 300psig) DWP

Corrosion protection

None

Internally epoxy coated

waterboxes and

tubesheets, sacrificial

anodes

Unit Configuration

Ability to isolate refrigerant charge in the

condenser

None

Isolation valves

Minimum load (assuming AHRI

unloading)

Down to 10% unloading

Down to 0% with hot gas

bypass

Unit mount

Neoprene pads

Spring isolation

Flow switches in the evaporator and

condenser water nozzles

Thermal flow switch or

differential pressure flow

switch

Ship loose paddle flow

switches

Unit paint

Caribbean blue paint

Amerlock 400, Amershield

Factory knock-down shipment options

Form 1 or 2

Form 3, 7, or 11

Unit wrapped before shipment

Partial wrapping (driveline

& electrical)

Complete chiller wrapping

Temporary shipping skids

None

Shipping skids

Long term storage requirements

None

Long term storage

Contact your local sales representative for more information.

Asia-source only

Europe-source only

Asia-source standard

Europe-source standard

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Application Data

The following is a guide to the application of YZ chillers to ensure reliable operation. While this guide is directed

towards normal, water-chilling applications, a Johnson Controls sales engineer can provide complete

recommendations on other types of applications.

LOCATION

YZ chillers are virtually vibration free and may generally be located at any level in a building where the construction will

support the total system operating weight.

The unit site must be a floor, mounting pad or foundation which is level within 6.5 mm (1/4") and capable of supporting

the operating weight of the unit.

Sufficient clearance to permit normal service and maintenance work should be provided all around and above the unit.

Additional space should be provided at one end of the unit to permit cleaning of evaporator and condenser tubes as

required. A doorway or other properly located opening may be used if convenient.

The chiller should be installed in an indoor location where temperatures range from 4.4°C to 40.0°C (40°F to 104°F).

The dew point temperature in the equipment room must be below the entering condenser water temperature to prevent

condensing water vapor inside of the VSD. Other areas susceptible to water vapor condensate are outside of the

condenser shell and condenser waterboxes. Example applications include cooling condenser water using chilled water,

wells, river, or other low temperature fluids.

Refrigerant Relief Piping - Each chiller is equipped with dual pressure relief valves on the condenser and two dual relief

valves on the evaporator, or two single relief valves on the evaporator if the optional refrigerant isolation valves are

ordered. The dual relief valves on the condenser are redundant and allow changing of either valve while the unit is fully

charged. The purpose of the relief valves is to quickly relieve excess pressure of the refrigerant charge, as a safety

precaution in the event of an emergency such as a fire. They are set to relieve at an internal pressure as noted on the

pressure vessel data plate, and are provided in accordance with local pressure vessel codes.

Sized to the requirements of applicable codes, a vent line must run from the relief device to the outside of the building.

This refrigerant relief piping must include a cleanable, vertical leg dirt trap to catch vent-stack condensation. Vent piping

must be arranged to avoid imposing a strain on the relief connection and should include one flexible connection.

Sound and Vibration Considerations - A YZ chiller is not a source of objectionable vibration in most air conditioning

applications. Standard neoprene isolation mounts are available with each unit to reduce vibration transmission. Optional

level-adjusting spring isolator assemblies designed for 25.4 mm (1") static deflection are also available for further

isolation. YZ chiller sound pressure level ratings will be provided upon request. Control of sound and vibration

transmission must be taken into account in the equipment room construction as well as in the selection and installation

of the equipment.

Thermal Insulation - The chiller’s cold surfaces should be insulated with a vapor barrier insulation sufficient to prevent

condensation. As an option, a chiller can be factory-insulated. This insulation will normally prevent condensation in

environments with dry bulb temperatures of 10.0°C to 32.2°C (50°F to 90°F) and relative humidity up to 75% [19 mm

(3/4") thickness], 85% [25.4 mm (1”) thickness], or 90% [38 mm (1.5") thickness]. It is intended for a chiller installed

indoors and, therefore, no protective covering of the insulation is usually required. If insulation is applied to the

waterboxes at the job site, it must be removable to permit access to the tubes for routine maintenance.

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Ventilation - Some standards requires that all machinery rooms be vented to the outdoors utilizing mechanical ventilation

by one or more fans. State, local and any other related codes should be reviewed for specific requirements. Since the

YZ chiller motor is hermetically sealed, no additional ventilation is needed due to motor heat.

In addition, the ASHRAE Standard 15 requires a refrigerant vapor detector to be employed for all refrigerants. It is to be

located in an area where refrigerant from a leak would be likely to concentrate. An alarm is to be activated and the

mechanical ventilation started at a value no greater than the Threshold Limit Value (TLV) of the refrigerant.

WATER CIRCUITS

Flow Rate - For normal water chilling duty, evaporator and condenser flow rates are permitted at water velocity levels in

the heat exchanger tubes of between 0.91m/s and 3.66m/s (3.0 fps and 12.0 fps) for evaporators and 1.0m/s and 3.66m/s

(3.3 fps and 12.0 fps) for condensers. Two pass units are also limited to 134kPa (45ft H

O) water pressure drop. The

three pass limit is 201kPa (67.5ft H

O). Variable flow in the condenser is not recommended, as it generally raises the

energy consumption of the system by keeping the condenser pressure high in the chiller. Additionally, the rate of fouling

in the condenser will increase at lower water velocities associated with variable flow, raising system maintenance costs.

Cooling towers typically have narrow ranges of operation with respect to flow rates, and will be more effective with full

design flow.

The chillers can tolerate a 50% flow rate change in one minute that is typically associated with the staging on or off of an

additional chiller; however a lower flow rate change is normally used for better system stability and set point control.

Proper sequencing via the building automation system will make this a very smooth transition.

Variable Primary Flow - There is increasing interest to use variable primary flow (VPF) systems in large chilled water

plants. VPF systems can offer lower installation and operating costs in many cases, but do require more sophisticated

control and flow monitoring. YZ chillers will operate successfully in VPF systems. With a minimum allowable evaporator

tube velocity of 0.5m/s (1.5 fps) for standard tubes at part load rating conditions, YZ chillers will accommodate the wide

variation in flow required by many chilled water VPF applications.

Temperature Ranges - For normal water chilling duty, leaving chilled water temperatures may be selected between

3.5°C (38°F) and 21.0°C (70°F) to obtain temperature deltas between entering chilled and leaving chilled water

temperature of 1.7°C up to 16.7°C (3°F up to 30°F).

Water Quality - The practical and economical application of liquid chillers requires that the quality of the water supply

for the condenser and evaporator be analyzed by a water treatment specialist. Water quality may affect the performance

of any chiller through corrosion, deposition of heat-resistant scale, sedimentation or organic growth. These will degrade

chiller performance and increase operating and maintenance costs. Normally, performance may be maintained by

corrective water treatment and periodic cleaning of tubes. If water conditions exist which cannot be corrected by proper

water treatment, it may be necessary to provide a larger allowance for fouling, and/or to specify special materials of

construction.

General Piping - All chilled water and condenser water piping should be designed and installed in accordance with

accepted piping practice. Chilled water and condenser water pumps should be located to discharge through the chiller

to assure positive pressure and flow through the unit. Piping should include offsets to provide flexibility and should be

arranged to prevent drainage of water from the evaporator and condenser when the pumps are shut off. Piping should

be adequately supported and braced independently of the chiller to avoid the imposition of strain on chiller components.

Hangers must allow for alignment of the pipe. Isolators in the piping and in the hangers are highly desirable in achieving

sound and vibration control.

Convenience Considerations - To facilitate the performance of routine maintenance work, some or all of the following

steps may be taken by the purchaser. Evaporator and condenser waterboxes are equipped with plugged vent and drain

YZ Engineering Guide

Form: 161.01-EG1 (0819)

)

connections. If desired, vent and drain valves may be installed with or without piping to an open drain. Pressure gauges

with stop-cocks and stop-valves may be installed in the inlets and outlets of the condenser and chilled water line as close

as possible to the chiller. An overhead monorail or beam may be used to facilitate servicing.

Connections - The standard chiller is designed for 1034 kPa (150 psig) design working pressure in both the chilled

water and condenser water circuits. The connections (water nozzles) to these circuits are furnished with grooves to

ANSI/AWWA C-606 standard for grooved and shouldered joints. Piping should be arranged for ease of disassembly at

the unit for tube cleaning. All water piping should be thoroughly cleaned of all dirt and debris before final connections are

made to the chiller.

Chilled Water - A water strainer of maximum 3.2 mm (1/8") perforated holes must be field-installed in the chilled water

inlet line as close as possible to the chiller. If located close enough to the chiller, the chilled water pump may be protected

by the same strainer. The strainer is important to protect the chiller from debris or objects which could block flow through

individual heat exchanger tubes. A reduction in flow through tubes could seriously impair the chiller performance or even

result in tube freeze-up. A flow switch is factory installed in the evaporator nozzle and connected to the OptiView™ panel,

which assures adequate chilled water flow during operation.

Condenser Water - The chiller is engineered for maximum efficiency at both design and part load operation by taking

advantage of the colder cooling tower water temperatures which naturally occur during the winter months. Appreciable

power savings are realized from these reduced heads. At initial startup, entering condensing water temperature may be

as much as 16.7°C (30°F) colder than the standby chilled water temperature.

MULTIPLE UNITS

Selection - Many applications require multiple units to meet the total capacity requirements as well as to provide flexibility

and some degree of protection against equipment shutdown. There are several common unit arrangements for this type

of application. The YZ chiller has been designed to be readily adapted to the requirements of these various arrangements.

Parallel Arrangement - Chillers may be applied in multiples with chilled and condenser water circuits connected in

parallel between the units. Figure 1 below represents a parallel arrangement with two chillers. Parallel chiller

arrangements may consist of equally or unequally sized units. When multiple units are in operation, they will load and

unload at equal percentages of design full load for the chiller.

Figure 1 – Parallel Evaporators (Evap.) Parallel Condensers (Cond.)

Cond. 1

Evap. 1

Cond. 2

Evap. 2

- Thermostat for Chiller Capacity Control

- Temperature Sensor for Chiller Capacity Control

YZ Engineering Guide

Form: 161.01-EG1 (0819)

)

Depending on the number of units and operating characteristics of the units, loading and unloading schemes should be

designed to optimize the overall efficiency of the chiller plant. It is recommended to use an evaporator bypass piping

arrangement to bypass fluid around evaporator of any unit which has cycled off at reduced load conditions. It is also

recommended to alternate the chiller cycling order to equalize chiller starts and run hours.

Series/Parallel Arrangement - Chillers may be applied in pairs with chilled water circuits connected in series and

condenser water circuits connected in parallel. All of the chilled water flows through both evaporators with each unit

handling approximately half of the total load. When the load decreases to a customer selected load value, one of the

units will be shut down by a sequence control. Since all water is flowing through the operating unit, that unit will cool the

water to the desired temperature.

Figure 2 – Series/Parallel Arrangement

Series Counter Flow Arrangement - Chillers may be applied in pairs with chilled water circuits connected in series and

with the condenser water in series counter flow. All of the chilled water flows through both evaporators. All of the condenser

water flows through both condensers. The water ranges are split, which allows a lower temperature difference or "head"

on each chiller, than multiple units in parallel. For equal chillers, the machine at the higher temperature level will typically

provide slightly more than half the capacity. The compressor on each chiller is often matched, such that the high

temperature machine can operate at the low temperature conditions when one unit is cycled off at part load (as compared

to series-parallel chillers which are typically not identical).

Figure 3 – Series Evaporators (Evap.) Series-Counter Flow Condensers (Cond.)

Cond. 1

Evap. 1

Cond. 2

Evap. 2

- Temperature Sensor for Chiller Capacity Control

- Thermostat for Chiller Capacity Control

Cond. 1

Evap. 1

Cond. 2

Evap. 2

- Temperature Sensor for Chiller Capacity Control

- Thermostat for Chiller Capacity Control

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York YZ Magnetic Bearing Centrifugal Chiller User guide

York YZ Magnetic Bearing Centrifugal Chiller User guide

York YZ Magnetic Bearing Centrifugal Chiller User guide

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